This invention relates to a magnetic recording/reproducing device such as a flexible disk drive.
As is well known, a flexible disk drive is a magnetic recording/reproducing device for carrying out data recording and reproducing operations to and from a flexible disk (hereinafter called a magnetic disk). In recent years, large capacity, magnetic disks have been developed. A typical magnetic disk has a storage capacity on the order between 1 Mbyte and 2 Mbyte (hereinafter called a normal capacity). In contrast, a magnetic disk having a storage capacity as large as 128 Mbyte (hereinafter called a large capacity) has already been developed. Following such increase in capacity of the magnetic disk, development is also made of a magnetic disk drive for carrying out data recording and reproducing operations to and from the magnetic disk of a large capacity.
In the following description, a magnetic disk drive capable of carrying out data recording and reproducing operations to and from the large-capacity magnetic disk alone will be referred to as a high-density dedicated magnetic disk drive. On the other hand, a magnetic disk drive capable of carrying out data recording and reproducing operations to and from the normal-capacity magnetic disk alone will be called a normal-density dedicated magnetic disk drive. A magnetic disk drive capable of carrying out data recording and reproducing operations to and from both the large-capacity and the normal-capacity magnetic disks will be called a high-density/normal-density magnetic disk drive. The high-density dedicated magnetic disk drive and the high-density/normal-density magnetic disk drive may collectively be called a high-density magnetic disk drive.
The normal-density dedicated magnetic disk drive and the high-density magnetic disk drive are different in mechanism from each other. One of the major differences resides in a drive source for driving a carriage holding a magnetic head. The drive source is for moving the carriage with respect to the magnetic disk inserted in the magnetic disk drive in a predetermined radial direction of the magnetic disk. Specifically, the normal-density dedicated magnetic disk drive uses a stepping motor as the carriage drive source. The stepping motor has a rotation shaft with a lead screw. On the other hand, the high-density magnetic disk drive uses a linear motor such as a voice coil motor (VCM) as the carriage drive source.
Now, description will be made in detail as regards the voice coil motor used as the drive source in the high-density magnetic disk drive. The voice coil motor is arranged at a rear side of the carriage. The voice coil motor comprises a voice coil wound around a drive shaft extending in parallel to the predetermined radial direction, and a magnetic circuit for producing a magnetic field in a direction intersecting electric current flowing through the voice coil. The voice coil is movable along the drive shaft. The magnetic circuit comprises a permanent magnet. When the electric current is made to flow through the voice coil in a direction intersecting the magnetic field produced by the magnetic circuit, drive force is generated in the voice coil in an extending direction of the drive shaft as a result of interaction between the electric current and the magnetic field. By the drive force, the voice coil motor makes the carriage move in the predetermined radial direction.
As is well known, the magnetic disk includes a magnetic disk medium accessed by the magnetic head. On each surface of the magnetic disk medium, a large number of concentric tracks are formed in a radial direction to record data. As will readily be understood, the large-capacity magnetic disk has a track width and a track pitch smaller than those of the normal-capacity magnetic disk. The tracks are successively arranged from an outermost track (hereinafter depicted at Tr00) to an innermost track. The outermost track Tr00 will herein be called an endmost track. The normal-capacity magnetic disk has 80 tracks on each surface.
When the magnetic disk is accessed by the magnetic head, the magnetic head must be positioned at a desired track location. For this purpose, it is necessary and sufficient to position the carriage holding the magnetic head.
In the normal-density dedicated magnetic disk drive adopting the stepping motor as the drive source, positioning of the carriage is easily achieved. This is because the carriage is driven by the stepping motor to move stepwise by a predetermined distance at every pulse applied thereto. Thus, no special positioning means is required in addition to the stepping motor.
On the other hand, in the high-density/normal-density magnetic disk drive adopting the linear motor as the drive source, special positioning means is required to position the carriage if the normal-capacity magnetic disk is inserted therein. This is because the linear motor is responsive to the electric current flowing through the voice coil to freely move in the predetermined radial direction so that any control is required in order to stop such free movement. Positioning of the carriage requires a carriage location detector for detecting a current location of the carriage and a carriage location controller for controllably moving the carriage to a desired location with reference to the current location detected by the carriage location detector.
In case where the large-capacity magnetic disk is inserted in the high-density/normal-density magnetic disk drive, it is unnecessary to use the above-mentioned positioning means. This is because, in the large-capacity magnetic disk, a servo signal for location detection is preliminarily written on the magnetic disk medium.
As will later be described in detail, a conventional carriage location detector requires manual adjustment for an initial setting operation. Such manual adjustment is troublesome.